Writing instrument



FIG. 1 is a left side perspective view of a writing instrument showing my new design;

FIG. 2 is a right side perspective view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a side view thereof, which is a mirror image of the opposite side thereof;

FIG. 6 is a rear view thereof; and,

FIG. 7 is a bottom view thereof.

The broken line showing of the writing tip illustrates environmental matter and forms no part of the claimed design.

The stippling shown in the drawings represents a texture on the surface of the pen. 

The ornamental design for a writing instrument, as shown and described. 